Turbine-blade fastening



May 25 1926; I 1 1,585,713

H. T. HERR ET AL TURBINE BLADE FASTENING fi'il d May 31', 1922 w /e\ A L.Z.Jmilh WITNESES2 I iNVENTOR ATTORNEY Patented May 25,

PAT? FFECE.

HERBERT T. HERB, OF PHILADELPHIA, AND LOUIS L. SMITH, 012'" RIDLEY PARK,

PENIJSYLVANIA, ASSIGNORS TO VJESTINGI-IGU3E ELECTRIC AND MANUFACTUR- ING COMPANY, A COBPQBATIGN OF PENNSYLVANIA.

TURBINE-BLADE FASTENING.

Application filed May 31,

Our invention relates to a turbine blade fastening particularly adapted for use with wide blades and-it has for its object to provide apparatus of the character designated which shall serve to develop a more effectively distributed holding force than in apparatus heretofore proposed and known to us.

In the accompanying drawing, Fig. 1 is a diagrammatic view of a portion of a turbine rotor provided with blades fastened in place in accordance with our invention; Figs. 2 and 3 are plan and elevational views of one form of compound wedge adapted to be used in this case; and, Figs. 1 and 5 are similar views of alternative form of compound wedge.

In the application of Alexander T. Kasley, Serial No. 527,674 filed January 7, 1922 and assigned to Westinghouse Electric & Manufacturing Company there is disclosed and claimed turbine blading of the wide exhaust type provided with root portions of the double dove tail type adapted to fit in correspondingly shaped longitudinal slots in a turbine rotor. In an application of Christian Gilson, Serial No. 554,988 filed April 18, 1922 and assigned to Westinghouse Electric & Manufacturing Company there is disclosed and claimed turbine blading of the wide exhaust type, made in sections for the purpose of facilitating the manufacturing thereof.

In an additional application of Christian Grilson, Serial No. 595,613 filed October 19, 1922. and assigned to Westinghouse Electric 85 Manufacturing Company there is disclosed and claimed a compound wedge for holding the blades in place, the Wedge being split on a plane slightly transverse to the holding slot so as to distribute a powerful holding force.

In accordance with the presentinvention, we find that, in certain instances, it is inadequate to provide solely a means for developing a transverse pressure against the blades inasmuch as slight inequalities in the height of the wedge and in the depth of the slot, tend to permit the fastening means to be come loose. We therefore propose, to employ a compound holding wedge slit on a plane sligthly inclined to the radius of the rotor as well as being slightly transverse to to the holding slot. Upon driving home a wedge of this type a pronounced radial force is developed as well as a force transverse of the slot, thus effectually preventing thedevice from becoming loose.

' liforeover, we find that, with'compound wedges of this type, there is a possibility of unequal distribution of the holding pressures because of slight imperfections in workmanship. We, therefore, propose that the abutting faces of one or more of the wedge elements of a compound wedge of the character designated shall be formed slightly convex so to premit a slight rocking motion of the wedge elements with the proper distribution of the holding forces.

Referring to the accompanying drawing for a more detailed understanding of our invention, we show a portion of a rotor or drum member at 10, Fig. 1. Suitable blades of the type disclosed in the aforementioned application are shown at 11 and 12, the blades being preferably made in sections 13.

The blade fastening slot is shown at 14 and comprises an upper wide portion having undercut side walls 15 and 16 and a deep, narrow central portion 17, having undercut side walls at 18 and 19.

The blades 11 are provided with upset root portions 20 adapted to set against the undercut side walls 15 and, similarly, the blades 12 have upset root portions 21 adapted to set against the undercut side walls 16. The compound wedge 22 is provided for lIlSGltlOIL between the roots 20 and 21 of opposed blades 11 and 12 in a slot 14 and to take in the slot 17 and it is formed of two complemental elements 23 and 24.

As shown more in detail in Figs. 2 and 3, the cleavage plane between the parts 23 and 241: is slightly inclined with respect to a radius of the rotor and is also slightly inclined to the longitudinal axis of the holding slot.

When assemblingth'e blading, the wedge 24- is first placed in position and the element 23 is then driven home; and, by virtue of the double inclination of the cleavage plane there is developed, not only a powerful trans verse wedge action tending to set the roots 20 and 21 firmly against the side walls 15 and 16, but there is also developed a powerful radial force tending to set the compound wedge member firmly in the holding slot 17 and also firmly engaging the roots 20 and 2L Because of slight imperfections in were manship it may occur that the holding; force developed by the wedge is not uniformly distributed. This difficulty may be obviated to a large extent by forming a wedge as shown in Figs. 4 and 5 in highly exaggerated form. The abutting faces of the wedge members 23 and 2d instead of being plane faces are slightly convex so as to permit a slight rocking action between the two members.

When inserted in place and driven home, the members 2 and 2st ma rock on each other to suitably distribute the holding forces in accordance with the predetermined design.

lVhile we have shown 'our invention in but two forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof, and we desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What we claim is:

1. In a turbine blade assembly, the combination with two blades seated against the opposite undercut walls of a holding slot of a blade holding element, respectively, of a two-part wedge member inserted therebetween and seated in a second slot, said wedge member being adapted to develop both a lateral and a radial thrust.

2. In a turbine blade assembly, the conr bination with a drum member provided with a relatively wide longitudinal slot having undercut side walls and having a relatively narrow longitudinal slot in the bottom thereof also having undercut side walls, of two blade members having enlarged root portions seated against the side walls of said wide slot, respectively, and a con'ipound wedge member disposed between said blade root portions and engaging therewith and als in said narrow slot, said wedge member being adapted to develop both a radial and a transverse thrust, whereby said blades are firmly attached to said drum member.

In a turbine blade assembly, the combination with a drum member provided with a relatively wide longitudinal slot having undercut side walls and having a relatively narrow longitudinal slot in the bottom thereof also having undercut side walls, of two blade members having enlarged root portions seated against the side walls of said wide slot, respectively, and a compound wedge member disposed between said blade root portions and engaging there with and also in said narrow slot, said wedge member being split on a plane slightly inclined with respect to a radial plane of said drum member, both radially and axially of said drum member, whereby when said wedge member is tightl assembled, it develops a thrust transversely of said slots and also vertically therein.

4. In a turbine blade assembly, the combination with blades seated against the opposite undercut walls of a holding slot provided in a blade holding element, respectively, of a two-part wedge member inserted therebetween and adapted to develop both a lateral and a radial thrust, the component part of said wedge being so shaped as to permit a slight mutual rocking motion, whereby the pressures developed at the dii ferent bearing points are automatically ad justed to predetermined relative values.

5. In a turbine blade assembly, he con-.- 'binat-ion with blades seated against the op posite undercut walls of a holding slot provided in a blade holding element, respectively, of a two-part wedge member inserted between the blades (nd adapted to develop both a lateral and a radial thrust, the component parts of said wedge being shaped as to permit a slight mutual rocking motion, whereby the 1 ressures developed at the different bearing points are automatically equalized.

6 In a turbine blade assembly, the combination with two blades seated against the opposite undercut walls of a holding slot provided in a blade holding element, respectively, of a two-part wedge member inserted between the blades and adapted to develop both a lateral and a radial thrust, at least one of the opposing faces of the component wedge elements being slightly convex, whereby a slight rocking and pressure-adjusting movement is permitted.

7 In a turbine blade assembly, the combination with two blades seated against the opposite undercut walls of a holding slot provided in a blade holding element, respectively, of a two-part wedge member inserted between the blades and adapted to develop both a lateral and a radial thrust, the opposing faces of the component wedge elements being slightly convex, whereby a slight rocking and pressure distributing movement is permitted.

8. In a turbine blade assembly, the combination with a drum member provided with a relatively widely longitudinal slot having undercut side walls and having a relatively narrow longitudinal slot in the bottom thereof also having undercut side walls, of two blade members having ei'ilarged root portions seated against the side walls of said wide slot, respectively, and a compound wedge disposed between said blade root por tions and engaging therewith and also in said narrow slot, said wedge being com prised by elements which are adapted to de velop both a radial and a tranhverse thrust, whereby said blades are firmly attached to said drum member and at least one of the coacting faces of the elements of said wedge members being slightly convex to permit a slight rocking, pressure distributing movement therebetween.

9. In a turbine blade assembly, the combination with a drum member provided with a relatively wide longitudinal slot having undercut side walls and having a relatively narrow longitudinal slot in the bottom thereof also having undercut side walls, of two blade members having enlarged root portions seated against the side walls of said wide slot, respectively, and a compound wedge comprising elements disposed between said blade roots and engaging therewith and. also in said narrow slot, said wedge being adapted to develop both a radial and a transverse thrust, whereby said blades are lirn'ily attached to said drum member, and the coacting faces of the elements of said wedge member being slightly convex to permit a slight rocking pressure-distributing movement therebetween.

10. In a turbine blade assembly, the combination with a drum member provided with a relatively wide longitudinal slot having undercut side walls and having a relatively narrow longitudinal slot in the bottom thereof also having undercut side walls, of two blade members having enlarged root portions seated against the side walls of said Wide slot, respectively, and a compound wedge member disposed between said blade roots and engaging therewith and also in said narrow slot, said wedge member being split on a plane slightly inclined with respect to a radial plane of said drum member, both radially and axially of said drum member, whereby when said member is tightly assembled, it develops a thrust transversely of said slots and also vertically therein, at least one of the wedge elements being slightly convex on said plane of cleavage, whereby a slight rocking, pressure-equalizing movement is permitted.

11. In a turbine blade assembly, the combination with. a drum member provided with a relatively wide longitudinal slot having undercut side walls and having a relatively narrow longitudinal slot in the bottom thereof also having undercut side walls, of two blade members having enlarged root portions seated against the side walls of said wide slot, respectively, and a compound wedge member disposed between said blade roots and engaging therewith and also in said narrow slot, said wedge member being split on a plane slightly inclined with respect to a radial plane of said drum member, both radially and axially of said drum member, whereby when said wedge member is tightly assembled, it develops a thrust transversely of said slots and also vertically therein, each of said wedge elements being slightly convex on said plane of cleavage, where by a slight rocking pressure-equalizing movement is permitted therebetween.

In testimony whereof, I have hereunto subscribed my name this 25th day of May,

HERBERT T. HERB.

In testimony whereof, I have hereunto 

